1. Field of the Invention
The present invention relates to a contact-type charger and an image forming apparatus provided with same.
2. Description of the Related Art
Conventional contact-type chargers used in copiers using electrophotographic methods have been proposed which use a polyurethane blade to remove residual charge remaining on the surface of a photosensitive member in preparation for a subsequent copy after a toner image formed on said photosensitive member has been transferred, such as the charger disclosed in Japanese Laid-Open Patent Application No. 57-48766.
Japanese Laid-Open Patent Application No. 49-72499 discloses art wherein a discharge sheet comprising a mix of carbon black and high molecular weight resin compound provided on a substrate cloth is used variously as clothing, carpet, wall covering, or industrially as an electrode in an electrostatic discharge device.
Japanese Laid-Open Patent Application No. 4-51265 discloses a contact-type charger that charges the surface of a photosensitive member by pressing a conductive member supported by a flexible member against said photosensitive member in an image forming apparatus.
Japanese Laid-Open Patent Application No. 4-51266 further discloses a contact-type charger that charges the surface of a photosensitive member via contact of a film-like charging member and the surface of said photosensitive member in an image forming apparatus.
These chargers all differ from typical corona-type chargers that charge a charge-receiving member such as a photosensitive member or the like via non-contact charging, inasmuch as charging is accomplished via contact between a charge-receiving member and a charging member formed of various materials in various configurations.
In contact-type chargers, foreign substance adhered to the surface of the charge-receiving member remains on a contact area due to the relative movement of the charge-receiving member and the charging member with keeping a contact state. Specifically, toner adhered to the surface of the photosensitive member remains on the contact area when charging is accomplished by devices that charge the photosensitive member via contact charger in image forming apparatuses of the electrophotographic type. In contact-type chargers, when foreign substance collects in the space formed between the charging member and charge-receiving member due to charging of the charge-receiving member via discharge, a suitable discharge cannot be generated such that the charge-receiving member cannot be uniformly charged, thereby producing uneven charging.
When a large amount of such foreign substance accumulates, the accumulated material overflows the local area and soils not only the charging device and charge-receiving member, but also the various peripheral components located nearby.